(a) Field of the Invention
The present invention relates to a liquid crystal display.
(b) Description of the Related Art
Liquid crystal displays (“LCDs”) are one of the most widely used flat panel displays. An LCD includes a pair of panels provided with field-generating electrodes, such as pixel electrodes and a common electrode, and a liquid crystal (“LC”) layer interposed between the two panels. The LCD displays images by applying voltages to the field-generating electrodes to generate an electric field in the LC layer that determines the orientations of LC molecules therein to adjust polarization of incident light.
An LCD also includes switching elements connected to the respective pixel electrodes and a plurality of signal lines such as gate lines and data lines for controlling the switching elements and thereby applying voltages to the pixel electrodes.
Among the LCDs, a vertically aligned mode LCD, which aligns the major axes of the LC molecules perpendicular to the upper and lower panels in the absence of an electric field, is spotlighted because of its high contrast ratio and wide reference viewing angle. Here, the reference viewing angle is defined as a viewing angle making the contrast ratio equal to 1:10 or as a limit angle for the inversion in luminance between the grays.
To implement wide viewing angle in the vertically aligned mode LCD, cutouts are provided in the field generating electrodes or protrusions are provided on the field generating electrodes. Since the cutouts and the protrusions can determine the tilt directions of the LC molecules, the tilt directions can be distributed into several directions by using cutouts and protrusions, thereby giving a wide reference viewing angle.
However, an increase in the number of cutouts and protrusions reduces the transmittance since it is hard for light to transmit where the cutouts or the protrusions are located. In order to increase the aperture ratio, an ultrahigh aperture ratio structure, in which the size of the pixel electrodes is increased, has been suggested. However, in this case, the LC molecules located in the central area of the pixel electrode are hardly affected by the electric field near the edges of the pixel electrode, which causes a disorder of the orientations of the LC molecules, and as a result, texture or light leakage occurs and the response time increases.
Therefore, a display device is required with improved response speed and transmittance of an LCD as well as an increase the aperture ratio of the LCD.